1. Field of the Invention
The present invention relates to a device for attachment to a mammalian subject in order to obtain data about one or more physiological parameters of the subject. In particular, the device relates to a physiological sensor device in the form of a patch attachable to the chest of a human subject to enable sensing of physiological data such as electro-cardiographic data and/or respiration data, and a method of manufacture thereof
2. Description of the Prior Art
The prior art includes U.S. Pat. No. 3,943,918 to Lewis which discloses an ECG signal sensing and transmitting device for use in the care of medical patients requiring monitoring of cardiac functions. The device disclosed is a single use, disposable unit consisting principally of a foam pad having a pair of circular electrodes in one face of the rectangular foam block. The block is attached using an adhesive layer to a patient and comprises electrical circuitry which transmits an RF signal to a receiver which is required to be within 100 feet of the patient. Subsequent filtering and amplification of the signal takes place at a monitoring station comprising a receiver and filter.
U.S. Pat. No. 4,121,573 discloses a chest sensor for monitoring cardiac rhythms of a patient using a pair of spaced circular electrodes mounted on a foam pad. Electrical connectors between the electrodes and electronic circuitry for acquiring and transmitting cardiac rhythm signals is provided by independent electrical leads or wires. The circuitry and wires are located on the rear surface of a first layer of foam and held in position by a second layer of foam. Accordingly, a fairly deep configuration of layers of foam, electronic circuitry and electrodes is provided. A radio frequency receiver and converter is provided within the vicinity of the transmitter which passes a signal to display equipment for enabling a user to view the cardiac rhythms of the patient.
U.S. Pat. No. 4,957,109 discloses an electrode array for use in generating electrocardiographic signals for a patient. The array comprises ten different electrode regions (comprises pairs of semi-circular electrodes) for attachment to different parts of the human body. The electrodes are interconnected to an output connector 2 for attachment to signal processing apparatus. The electrode sensors and electrical conductors between the electrodes and the output conductor are formed on a flexible circuit board having a large dentritic or tree-like configuration to enable location of the electrodes at the appropriate positions on the human body for standard twelve lead diagnostic electrocardiogram studies. Accordingly, electrical connection from one electrode through to the output connector passes around one or more different electrode sensors on the flexible circuit board requiring a complicated arrangement of insulating material in order to try to prevent short circuiting between a sensor and surrounding electrical connections.
U.S. Pat. No. 5,634,468 discloses a sensor for physiological monitoring of a patient, consisting of a rectangular patch having a central structural member formed of MYLAR(trademark) encased in an adhesive hydrogel. One side of the sensor has four circular electrodes for contacting the patient. The electrodes are wired to an electronic package on the opposite side of the structural member. The electronics package is adapted to receive ECG data and transmits the data to a monitoring unit. Such a small sensor is limited to measuring ECG signals.
U.S. Pat. No. 5,353,793 discloses sensor apparatus for making ECG measurements comprising a band which passes entirely round a patient""s chest. The chest band can have optional shoulder straps and an optional abdominal band. Electrodes are positioned around the inner circumferential surface of the band for monitoring respiration, pulse and ECG signals. The ECG electrodes are simple conductive sensors in electrical contact with the skin. The pulse and respiration sensor comprises a tension sensor consisting of a piezoelectric element. A minimum of 7 ECG sensors is provided but up to 18 can be spaced around the band. Two or more of the piezoelectric sensors can be provided in a single chest band. The various sensors are connected by cabling and accordingly the apparatus as a whole is considerably bulky to wear.
International patent specification WO94/01039 discloses physiological monitoring apparatus having a strip assembly for attachment to a patient""s chest. The strip comprises a series of nine electrically conductive electrode sensors for attachment to the precordial region of a patient""s chest for obtaining ECG data. The strip is relatively complex and comprises a plurality of recesses for individual electrodes for example.
An object of the invention is to avoid or at least mitigate problems of the prior art. In particular, the invention seeks to provide an improved physiological sensor device which is easy to attach to a subject and/or comfortable to wear and/or disposable after a single use over, for example, a 24 hour period. Another object is to provide a device which is relatively simple to manufacture while enabling collection of accurate data. A further object of the invention is to provide a device which is able to collect a variety of types of physiological data, such as ECG, respiration, motion and temperature, for example, while still being relatively inexpensive to manufacture.
A first aspect of the invention provides a physiological sensor device for attachment to a mammalian subject comprising two regions of sensors attachable to a subject in use, which regions are separated by a flexible web adapted to enable variable separation of the two sensor regions from one another in use. Beneficially, the two sensor regions are attachable in precordial positions, substantially horizontally aligned, on a human chest, and the flexible web enables the subject to breathe and move easily after attachment of the device, in spite of expansion and reduction in chest size when breathing or moving.
Preferably the web comprises an outer layer which operably contacts a subject which layer does not adhere to the subject in use thereby to aid the increased flexibility of the device. Preferably, when unbiased, the flexible web has a neutral position which fixes the separation of the first and second sensor regions to a predetermined length. The flexible web further comprises a position indicator such as a substantially V-shaped portion. The V-shaped portion can be formed of two arms which subtend an angle of between of 60 and 130xc2x0 and more preferably between 100 and 120xc2x0, and in one form an angle of 115xc2x0. The separation of the first and second regions in the unbiased position of the web can be between 20 and 200 mm and more preferably between 40 and 130 mm.
A third region of sensors attachable to the subject can be provided which region is separated from one of the first region and second region by a second flexible web. The second flexible web preferably also does not adhere to the subject in use. The third region can be adapted to attach below the axilla of a subject. Accordingly, the second web can be adapted to pass over the pectoral region of the subject. Preferably the length of the second web in the mutual unbiased position is between 20 and 200 mm and more preferably between 50 and 10 mm. The second web can subtend an angle to the first or second region of between 30 and 60xc2x0 and more preferably about 45xc2x0.
Preferably, electrode sensors on the first region and second region are aligned on a transverse axis across both the first and second regions. This provides benefits in the ease of manufacture of the device as described later.
In another embodiment, a physiological sensor device can be provided for attachment to a mammalian subject comprising a first and second electrode sensor in spaced separation along the transverse axis of a region of the device, wherein the first and second electrode sensors are mounted on a flexible substrate.
The first and second electrode sensors can comprise electrically conductive ink printed on a flexible substrate. Preferably, the conductive ink is substantially non-polarizing and may comprise, for example, a silver/silver chloride ink.
The first and second electrode sensors are separated by a slot in the flexible substrate. A strip of conductive gel can be positioned over the first and second electrode sensors which conductive gel is also divided by a slot passing therethrough.
Another form of the invention provides a physiological sensor device for attachment to a mammalian subject comprising a region having at least one physiological sensor and a layer of adhesive for attachment of the region to the subject in use, wherein the region comprises at least one slot enabling greater flexibility in the region when worn by the subject in use.
A yet further aspect of the invention provides a physiological sensor device for attachment to a mammalian subject comprising an electrode sensor comprising a region having at least one electrode sensor comprising a layer of electrically conductive gel attachable to the subject in use, the region further comprising a layer of non-conductive adhesive also attachable to the subject in use. Preferably the electrically conductive gel also has adhesive properties. The gel can for example be a hydrogel, while the non-conductive adhesive can, for example, be hydrocolloid. In a preferred embodiment, two strips of non-conductive adhesive are provided adjacent opposite sides of a strip of electrically conductive gel.
A further aspect of the invention provides a physiological sensor device comprising a region having one or more sensors attachable close to a subject""s axilla wherein the region comprises electrical circuitry for processing physiological signals from the one or more sensors. Preferably, the region comprises an output transmitter, such as a substantially flat coil antenna, for communicating the physiological signals to a remote location. Preferably, one of the sensors comprises a temperature sensor. Beneficially, this region can carry electrical circuitry for processing physiological signals from the one or more sensors and can be accommodated in the space between the wearer""s chest and arm.
According to a further aspect of the invention there is provided a method of manufacturing a physiological sensor device having two or more electrode sensors, comprising the steps of forming a strip of electrically conductive material on a flexible electrically non-conductive substrate, and cutting a slot through both the flexible substrate and conductive strip to define a pair of adjacent edges of conductive material separated by a non-conductive gap thereby also to define adjacent electrode sensors each having one of said pair of adjacent edges formed in the strip of conductive material.
Preferably the step of forming a strip of conductive material comprises printing a layer of conductive ink onto the flexible non-conductive substrate. The method can comprise the step of laying a strip of electrically conductive gel over the strip of electrically conductive material prior to the step of cutting a slot therethrough.
Another aspect of the invention provides a method of manufacturing a physiological sensor device having a plurality of electrode sensors, comprising the steps of forming a series of electrode sensors axially separated one from another along a common axis, forming a layer of conductive gel over all the axially aligned electrode sensors using a single strip of conductive gel, and forming separate areas of gel over each sensor by cutting through the layer of gel between each of the electrode sensors in the series. Preferably the method further comprises the step of providing electrical isolation between one or more of the electrode sensors in the series by cutting slots in the flexible substrate to which the electrodes are mounted.
A further aspect of the invention provides a physiological sensor device for attachment to a mammalian subject, having a laminate structure comprising:
a flexible non-conductive substrate,
an arrangement of electrically conductive tracks formed on the substrate,
an electrical device such as a physiological sensor or electronic circuit (PCB), electrically conducted to one or more of the electrically conductive tracks by an electrically conductive adhesive, and
a backing layer covering at least part of the arrangement of conductive tracks and attached to at least part of the flexible non-conductive substrate.
Preferably the conductive adhesive has a relatively low electrical resistance in one direction and a relatively high electrical resistance orthogonal thereto.
A yet further aspect of the invention provides a method of attaching a physiological sensor device comprising a patch attachable to a subject, which patch comprises a first and a second sensor region, separated by a flexible web, comprising the step of positioning the first sensor region in a precordial position on the chest and positioning the web over the subject""s sternum thereby to locate the second sensor region on the right side of the subject""s chest.
A yet further aspect of the invention provides a method of attaching a physiological sensor device comprising a patch attachable to a subject, which patch comprises a first sensor region attachable to a precordial position on a subject""s chest, and another sensor region attachable to below the subject""s axilla, where the first and another sensor region are separated by a flexible web, comprising the step of positioning the another sensor region below the subject""s axilla and then positioning the first sensor region in a precordial position on the subject""s chest by passing the flexible web over the subject""s pectoral muscle. Preferably, the web comprises a position indicator and the method comprises the step of positioning the position indicator centrally on the sternum prior to attachment of the first and second sensor regions to the chest.
Also, the device can comprise a third sensor region separated from one of the first and second sensor regions by a second flexible web, the method further comprising the step of locating the third sensor region below the subject""s axilla and passing the second flexible web over the subject""s pectoral muscle. Preferably, the first, second and third sensor regions each comprise an electrode for measuring ECG and wherein the method of attachment of the three sensor regions enables the electrodes to be positioned on a subject in use so as to approximate an ECG lead II for ECG signal acquisition.
Another aspect of the invention provides a method of attaching a physiological sensor device comprising a patch attachable to a subject, which patch comprises a first sensor region attachable to a precordial position on a subject""s chest, and another sensor region attachable to below the subject""s axilla which first and another sensor region are separated by a flexible web, comprising the step of positioning another sensor region below the subject""s axilla and then positioning the first sensor region in a precordial position on the subject""s chest by passing the flexible web over the subject""s pectoral muscle.
Other inventive features of the invention will become apparent from the following description. Moreover, the invention provides a device, method of manufacture thereof, or method of attachment thereof to a user comprising any one of the individual features herein described (including any individual parameter within any specified ranges) or any combination thereof.